Four wheel alignment parameters affect the tire performance measurement

In a recent test drive we installed a set of Goodyear Eagle F1 GS-3D tires called cuff flying boots. This tire is a product that balances comfort and dry performance. The user's attention and favor. After our two-week test drive, we found that the car will experience a siring sound when the speed is between 30-40km/h. For this reason, we feel very surprised, is the coupe running boots is undeserved reputation? After some inspection and testing, spearhead pointed to the car's four-wheel positioning parameters. Therefore, we have compared the measured tire performance before and after adjusting the four-wheel alignment.

Measured wonderful pictures:

Four wheel alignment analysis:

1. Introduction of four-wheel alignment parameters:

(Left angle a is the main caster; right angle B is the main caster)

(Left on the various toe diagrams; on the right, angle a is the tire camber)

The front wheel positioning includes the four contents of the kingpin caster, the kingpin caster, the front camber, and the front wheel toe .

Rear wheel alignment includes wheel camber and rear wheel toe .

Front-wheel positioning and rear-wheel positioning are collectively called four-wheel positioning.

Generally speaking , the caster and caster angles are related to the vehicle suspension components. They have been designed during vehicle design and cannot be changed under normal circumstances.

The front and rear camber angles of the front and rear wheels can be adjusted by a certain mechanism.

Here are two parameters that are most closely related to the maintenance of the four-wheel alignment of our vehicle - camber angle and toe-in .

2. Camber:

Today's cars generally use flat radial tires (tires with high tread rigidity and wide tread). Under normal circumstances, only a small negative camber is set (negative camber angle: the vehicle wheel is seen from the front and rear, showing the shape of "eight"). In order to give the wheel bearing proper lateral pressure to combine it more closely reduce the internal vibration of the bearing. The camber angle also affects the steering characteristics of the vehicle to some extent.

3. The first beam:

Today's cars generally set the front torsion of the wheels to be forward torsion (front toe: assume that the forward direction of the car is forward, the front end of the coaxial wheel) to give the vehicle and the steering wheel an appropriate return moment.

4. When to adjust the four-wheel alignment:

In general, we need to perform four-wheel alignment of the vehicle in the following situations.

1) After replacement of new tyres or maintenance of collision accidents;

2) unilateral abrasion of front and rear tires;

3) The steering wheel is too heavy or flutters when driving;

4) When the car goes straight, it will go to the left or right;

5) Although there is no such situation, for the purpose of maintenance, it is recommended that the new vehicle should check the four-wheel alignment parameters every six months or 10,000 kilometers after driving for 3 months.

Actual four-wheel alignment adjustment:

After the inspection of the four-wheel locator, the toe of the rear wheel of this vehicle deviated from the standard value, and there was no problem with the parameters of the camber of the front and rear wheels and the front toe of the front wheel. Please see the figure below for detailed data.

(Checked front wheel toe parameters)

(Four-wheel alignment parameters after adjustment of front wheel toe data)

(The maintenance master adjusts the front wheel of the rear wheel)

When adjusting the four-wheel alignment parameters, the maintenance engineer adjusts the front arm thread and the tilt arm eccentric nut based on the data on the four wheel alignment indicator. The four-wheel alignment adjustment seeks to adjust the data to the standard value, and adaptability is adjusted according to actual test conditions.

After the four-wheel alignment data is adjusted within the standard range, it is also required to test the vehicle to determine whether the steering wheel is biased. If the offset is required, the steering wheel or the front beam arm needs to be adjusted so that the steering wheel is positioned straight when the vehicle goes straight.

Site measurement:

We performed an acceleration test of 60km/h and a 45km/h boring test before and after adjusting the four-wheel alignment parameters.

Acceleration brake test of 60km/h: Test the longitudinal grip of the tire.

45km/h reel test: Test the lateral grip of the tire.

The test site is a newly paved asphalt pavement (dry land); the test temperature is 5-10 degrees Celsius on the day of testing.

In carrying out the above two tests, we used the speed limit function that the car had. The speed limit would be forbidden after the speed reached the predetermined speed, and a more accurate constant speed was achieved.

Test data analysis:

The red curve is the parameter before the four wheel alignment adjustment, and the green curve is the parameter after the four wheel alignment adjustment.

From the above figure, we can see that after the four-wheel alignment adjustment to reasonable data, the absolute acceleration of the maximum acceleration of the full throttle is 0.51G, which is 0.1G higher than before the adjustment, and the vertical grip is obviously improved. In the same way, we can see that the absolute value of the absolute acceleration peak value during emergency braking is not much different before and after adjusting the four wheel alignment parameters. However, we found that after adjusting the four-wheel alignment parameters, the absolute value of the longitudinal acceleration fluctuations around the peak value of the absolute, remove the impact of ABS, we believe that the cause of this phenomenon is that the rear brake pads have reached the wear limit (this point in the further inspection of the vehicle brake pads Was verified.

From the above figure, we can see that the pile is tested at the same speed on the same site. The correct four-wheel positioning parameters make the longitudinal grip of the vehicle get a certain increase. The range of the green curve measured after adjustment of the four-wheel alignment in the longitudinal coordinate is wider than the range of the curve before the adjustment, which also reflects the significant improvement of the longitudinal grip.

to sum up:

Many people feel that it is of little significance to carry out four-wheel alignment checks and adjustments; however, from the data measured in this paper, good four-wheel alignment parameters do improve the vehicle's maneuverability and enhance the vehicle's active safety. At the same time, a good four-wheel positioning parameter can also extend the service life of the suspension and wheels, and reduce the damage due to component damage. Therefore, it is very necessary to regularly check the vehicle's four-wheel alignment parameters.